Interlocking mechanism for electric switches



p 7, 1943 K. M. HAMMELL 2,328,801

INTERLOGKING MECHANISM FOR ELECTRIC SWITCHES Filed Dec. 2, 1940 5 Sheets-Sheet l gwue/wim 3&5 QQW S p 7, 1943- K M. HAMMELL 2,328,801

INTERLOCKING MECHANISM FOR ELECTRIC SWITCHES Filed Dec. 2, 1940 3 Sheets-Sheet 2 PIE. 5.

@W Mwmzz p 7. 1943- K. M. HAMMELL 2,328,801

INTERLOCKING MECHANISM FOR ELECTRlC SWITCHES Filed Dec. 2, 1940 3 Sheets-Sheet 3 Patented Sept. 7, 194a m'raanooxmo amonamsu ron ELECTRIC swrronas I Kemper M. Hammell, Toledo, Ohio, minor to The Swartabaugh Manufacturing Company, Toledo, Ohio, a corporation of Ohio Application December 2,1940, Serial No.'368,170

9 Claims.

mon hot-plate has a total capacity in excess of the allowable maximum if all of the units are turned to the high position, so that it is the usual practice to provide some means to prevent the user from turning the switches which energize the several units to such a position that the allowable maximum will be exceeded. Taking, for example, the common two-element hotplate, each element may have a heating capacity of 1000 w. on high" and 600 w. on medium. It is obvious that one element may be used on high" and the other on medium" simultaneously, but that if both elements are turned to high the 1600 w. maximum will be exceeded.

The common practice has been to interlock the switches electrically or, in most instances, to provide some means whereby the act of turning one of the switches to high will open the circult of the other unit. Another frequent proposal has been to arrange the switches in such relation that the act of turning one unit to h1sh" interposed a dog or latch in the path of the other switch in the ofl" position preventing its movement. Prior devices have therefore been characterized by the disadvantage that when one switch was standing in or turned to the high" position, the other switch was either turned off or locked against movement to any of its heating positions. "The primary object of the present invention is the provision of an eillcient and simple means to interlock two or more switches of an electric appliance in such a manner that, if one of the switches is standing in the "high position, the act of turning another switch to its high" position will result in a movement of the first switch to a position in which its element consumes less power as, for example, the "medium" position.

- Another object of the inventionis the provision of a simple and efficient interlocking mechanism for two switches, whereby-movement of one to a predetermined position causes a corresponding reverse movement of the other from a predetermined position,.each oi the switches be ing free to move to any position at any time.

Other objects and advantages of the invention will become apparent as the description proceeds, reference being had to the accompanying drawings, in which- Figure 1 is a front elevation, with parts broken away, of a switch interlocking mechanism incorporating the present invention: Fig. 2 is a section on the line 22 of Fig. 1-; Fig. 3 is a fragmentary diagrammatic representation of a modiiication; Fig. 4 is a fragmentary diagrammatic elevational view of a further modification; Figs. 5 and 6 are motion diagrams for the form of the invention shown in Figs. 1 and 2, showing the parts in various positions; Fig. 7 is a diagrammatic view illustrating a variation in the motion transmitting apparatus; Fig. 8 is a diagrammatic front view of the invention applied to a toggle type switch, and Fig. 9 is a side view of the parts shown in Fig. 8.

Referring to the drawings, and particularly to the form shown in Figs. 1, 2, 5 and 6, the invention is shown as applied to two four position switches A and B which may be used for any electrical appliance in which the four positions are useful. The switches shown are of the snap acting type commonly used with hot-plates and ranges. The switch elements-are shown only diagrammatically since the present invention relates entirely to the operators therefor.

Each switchhas, of course, a rotatable shaft l0 carrying certain of the switch parts and extending through the front plate or panel I: to

- carry a dial it on which are imprinted the usual legend-s, on, i gh m dicate the heat at which the associated element is operating.

Fixed rigidly to the respective shafts I 0 are similar cams l 8' and It", each of which has a base circular portion andan extending lobe. Driver members It, iii are associated with the cams and preferably comprise pivoted rollers to reduce the friction between the parts. In the form under consideration the drivers l8, It" are carried at opposite ends of a lever 20 pivoted at its center on a fulcrum 22. The lever 20 is so arranged that one driver stands against the base circular portion of one cam when the other driver is in engagement with the lobe of its cm. The length of the lever arms, that is, the distance between the centers of the drivers i8- and the fulcrum of lever 20, is fixed so that when a cam is standing with its lobe under a driver, the center of the driver is offset with respect to the cam. and the offset is, in the form shown, opposite to the direction of intended movement. In Fig. 1 it will be seen that the driver associated with switch A is standing on the lobe 01' its cam, but that its center is slightly to the left of the extreme top of the cam. Therefore, it the lever were to be moved to force the driver It downwardly, the driver could move only if the cam under it turned in a clockwise direction.

' The operation of the interlock is apparent. As shown in Fig. 5, with cam it turned to a position such that its driver rests on the circular portion and cam li standing with its lobe under the driver li switch A is on "medium" and switch B is on high." If the user wishes to turn switch A to high, cam i6 moves its lobe upwardly, forces driver I87 up, lever 20 pivots about its fulcrum and driver l8 must move down. The only way driver i8 can move down is to force its cam il to turn. The center of the driver being oifset with relation to the center of the cam li the driver presses the cam around its center. The turning movement of the cam 16' causes switch B to go from high to medium."

Obviously, the converse is true, as shown in Fig. 6. Here switch A is shown standing on "high" and switch B on "medium. Movement of cam li to the dotted line position, toward high, causes a movement of cam 16' toward med-111m),

The form of the invention so far described utilizes a leverage transmitted force to interlock the switches. The force may also be transmitted by a member in compression or by a member in tension. Fig. 3 shows a compression bar carrying drivers 3| and 3| adapted to move and be moved by cams 32, 32 The centers of the drivers are offset with relation to the centers of their associated cams so that as the bar 30 is moved in a direction against a cam lobe, the cam (and switch) will turn in response to lateral movement of the bar.

Fig. 4 shows a tension member connected at its ends to slide members Il and l Each slide member carries a respective driver 42-, 42 and each is slotted to receive the shaft of the associated switch on which cams 43' and 43 are mounted. Taking the parts in the position shown, movement of cam 43 to a position .wherein its lobe would abut driver 42* causes slide II- to pull down on the tension member which transmits the force to driver I! and hence moves cam 43 out of its high" position.

The description has been confined entirely to those situations in which one or the other of the switch carried cams would stand in "high position. It will be apparent that so long as neither switch cam attains this position each moves entirely independently of the other and the switches are not interlocked.

In the forms so far described the movement oi the switch being turned down has been produced by the interaction of cams and drivers contacting each. other at a point oflset with relation to the center of the shaft to be turned. Obviously, the point of contact might be shifted so long as the resultant of the force between the driving and driven members remained eccentric. For example, as shown in Fig. 7, an inclined member 60 may cooperate with a roller 62 carried at the end of a crank arm 84 which is, in turn, fixed to the switch shaft. The wedging action produced by moving the inclined member II at right angles to the shaft axis will cause the shaft to turn. The operation of this form is the same as the operation of the form shown in Fig. 3.

In the case of a multi-position toggle switch, the invention may take the form shown in Figs. 8 and 9. As indicated in Fig. 9, the switches ll and may have three positions designated 011" "Low" and High corresponding to the heat of an associated electric unit. Each switch is provided with an extending operating finger ll, Il so that it may be moved to its various positions. The interlocking mechanism for the switches includes a pair of bell crank levers I2, 82*, pivoted at 83,13, and having their ends tied together by a bar 34. Each bell crank lever has an extending arm 85, which engages the operating finger o! the respective associated switch. The length of the tie bar and the disposition of the bell-crank levers are such that when the switch finger ll is moved to "high position, as shown in Fig. 8, the arm 85 of bell crank lever 82 must stand in the position corresponding to the reduced heat of switch 80. It will be seen that in the event the operator moves switch finger 8! to high position, the system of bell crank levers and connecting bar 84 will move switch finger 8i back irom its high" position to the next lower heat.

It will be understood that in every instance the interlocking mechanism described is capable of acting on and moving the operator or operating element of each of a plurality of switches from "high" position to a position in which the associated units give oil a lower heat when a companion switch is moved to a predetermined high position, but in no instance is the interlocking mechanism capable of moving any switch to the off position or blocking a switch to prevent its movement to high position. These are the two characteristics which have been so disadvantageous in devices with which I am familiar,

While the invention has been described in a specific environment and with a particular form and disposition of the parts, it will be appreciated that it is capable of diverse uses and modiflcations without departing from the scope and spirit or the appended claims.

What I claim as original and desire to secure by United States Letters Patent is:

1. In combination with a plurality of switches for electric heating units or the like, each 01 which switches has a high position, a lower position, and an 01! position, corresponding to the several degrees of energization of the associated heating unit, an interlocking mechanism including a cam carried by and movable with each switch, and means to move one cam by movement of another including a pivoted lever and drivers carried on each end of the lever and engageable by said cams, the fulcrum of said lever and the length of the lever arms being such that movement of one cam to high position will cause movement of a cam standing in high position to the lower position.

2. In combination with a plurality of rotatable switches for electric heating units or the like, each of which switches has a high position, a lower position, and an oil! position, corresponding to the several degrees of energization of the associated heating unit, an interlocking mechanism including a cam carried by each switch, a driver associated with each cam and, when said cam is turned to present its lobe to the driver, standing offset with respect to the center of rotation of the cam, and means connecting the drivers which said connecting means comprises a memher in tension.

6. In combination with a plurality of rotatable switches for electric heating units or the like, each of which switches has a high position, a lower position, and an off position, corresponding to the several degrees of energization of the associated heating unit, an interlocking mechanism including a rotary operator carried by each switch and means disposed between said rotary operators whereby either switch is caused to move in a predetermined direction from its high position to a lower position when the other switch is rotated in either direction into its high position.

7. In combination with a plurality of rotatable switches for electric heating units or the like, each of which switches has a high position, a lower position, and an off position, corresponding to the several degrees of energization of the associated heating unit, an interlocking mechanism including a rotary cam carried by each switch motion transfer means disposed between said cams so disposed that either switch is automatically moved in a predetermined direction from its high position to a lower position when the other switch is turned-in either direction to its high position.

8. Interlocking mechanism for switches for electric heating units or the like, each of which switches has a relatively high position, a lower position, and an off position, corresponding to the several degrees of energization of the associated heating unit, said interlocking mechanism including an operator carried by each switch, and means interconnecting the operators and operated by movement of one switch to high position to move another switch previously in high position to a lower position, between high and off.

9. Interlocking mechanism for switches for electric heating units or the like, each of which switches has a relatively high position, a lower position, and an off position, corresponding to the several degrees of energization of the associated heating unit, said interlocking mechanism including a cam carried by and movable with each switch, and means operated by one cam when its associated switch is moved to high position, to move a cam and associated switch previously in high position to a lower position.

IEMPER M. HAMMELL. 

